Docs: copy/pasta left a type annotation from the IDLs in an example

sky/examples/style/hex-layout.sky

Index: sky/examples/style/hex-layout.sky
diff --git a/sky/examples/style/hex-layout.sky b/sky/examples/style/hex-layout.sky
index 695c2dd4029c797cca552a20e7d6f167f4e3b007..1d98c1d4c45d1432534920f12335ff0faf4e6745 100644
--- a/sky/examples/style/hex-layout.sky
+++ b/sky/examples/style/hex-layout.sky
@@ -84,7 +84,7 @@
      }
      return super(height); // does the equivalent of getIntrinsicWidth() above, applying min-height etc
    }
-   function paintChildren(RenderingSurface canvas) {
+   function paintChildren(canvas) {
      let width = this.node.width;
      let cellCount = this.node.getProperty('beehive-count');
      let cellDim = width / cellCount;